Originally Posted by Fishie
Thanks!! I didn't want them to hybridize though.
... to prevent livebearing fish (Guppy, Platy, Molly, Swordtail) from hybridizing is to only keep the same gender together. If you mix males and females together and with other livebearing fish of the same specie (ie other guppies, or platys,etc) there's nothing you can do to stop them.
If you are trying to keep your strains "true" only keep that one strain in the tank or only the same gender from all the varieties of the same specie. They can't breed outside their specie (sans my 1 experience mentioned above.)
Keep in mind that if you keep the offspring from this first pairing, they will carry the genes of the 2 colors so these would not be good candidates for selective breeding.
Hope this clears things up for you.